How to make bird-friendly windows

Daniel Klem has been studying bird strikes against windows for four decades. The Minnesota Vikings' new stadium will be nearly 40 percent glass, and the team will not spend $1.1 million for bird-safe glass.

The NFL's Minnesota Vikings created quite a flap in birding circles recently by refusing to make their next stadium bird-friendly.

Even though the stadium is being built along a migratory route used by tens of millions of birds every year, and birds can fly into most glass because they cannot see it, the stadium's exterior will be almost 40 percent reflective glass — roughly 200,000 square feet.

The Vikings could use a type of glass that's safer for birds, but it would cost an estimated $1.1 million. They say no dice.

Although more than 60,000 bird-lovers have signed an online National Audubon Society petition in protest, it is uncertain whether the Vikings will have a change of heart.

Like charity, however, bird conservation should also begin closer to home. How can backyard bird-watchers reduce bird strikes at their own windows?

For answers, I turned to Daniel Klem, a leading advocate for bird-safe windows and a professor at Muhlenberg College in Pennsylvania. He has studied the problem for four decades, including research in the 1990s that showed that between 100 million and a billion birds were killed by flying into buildings every year. "Based on the evidence we've been able to gather since then, I now think the figure is closer to 1 billion," he says.

One reason, Klem says, is that people have a disconnect when it comes to birds and windows. "When people think of conservation disasters, they think of the oil spill in the Gulf of Mexico or the Exxon Valdez spill in Alaska," says Klem, "even though it would take 333 Exxon Valdezes every year to equal 100 million birds killed in window strikes."

Yet few folks are talking about making windows safer.

"I love windows as much as anybody else," Klem says. "We just need to make them safe. We have the technology and the means. We just need to apply it."

For large new buildings, that means glass with special coatings or patterns visible only to birds.

But backyard bird-watchers can take a few simple steps to reduce bird strikes as well. Because every window can act like a perfect mirror on the exterior, Klem says, he suggests putting up decals, drawings or stickers on the outside of windows. "If you put them up on the inside, birds won't see them because the reflection on the outside masks them."

Birds are also less likely to fly into dirty panes: "The Lincoln Park Zoo in Chicago was the first institution I am aware of that purposely 'soaped' their windows during the migratory periods to reduce the window threat to birds passing through their grounds."

If you insist on clean windows, you might think twice about where you place your bird feeders. Klem did a study on that as well.

"We documented that the closer to the window you put the feeder and watering areas, the more birds' lives you'll save," the professor says. "Within 1 meter of the window, you're not going to get any kills. A bird that's farther than 3 feet away can leave a perch and build up enough momentum to kill itself outright when it strikes your glass."

The one drawback to moving your feeder closer to your window is those dreaded squirrels will have easier access, but as Klem points out: "If you have a bird feeder, you also have a squirrel feeder."

His advice to the Vikings regarding their next stadium is simple. "You're building a bird killer," he says. "Is that what you want your beautiful structure to represent? Surely you must take some steps to make it safe for these animals and still make a wonderful entertainment venue for all those who enjoy football."